TWI904213B - workpiece processing sheet - Google Patents

Abstract

A workpiece machining sheet is provided that exhibits excellent pick-up and excellent antistatic properties even when using an active energy radiation non-curing adhesive layer.

A workpiece processing sheet 1 comprises a substrate 11 and an adhesive layer 12. The substrate 11 includes a surface layer 111 near the adhesive layer 12, a back layer 113 away from the adhesive layer 12, and an intermediate layer 112 between the surface layer 111 and the back layer 113. The adhesive layer 12 comprises a non-curing adhesive with active energy radiation. The surface layer 111 and the back layer 113 contain antistatic agents. When the substrate 11 is subjected to a tensile test at a temperature of 23°C and a relative humidity of 50%RH, the tensile stress at 20% and 50% elongation is 8 MPa or more and 30 MPa or less, respectively.

Description

Workpiece machining sheet

This invention relates to a workpiece processing sheet used in the processing of workpieces such as semiconductor wafers.

Semiconductor wafers made of silicon, gallium arsenide, etc., and various packages are manufactured in large sizes. After being diced into chips and picked up, they are transferred to the next assembly process. At this time, the semiconductor wafers and other workpieces are laminated on an adhesive sheet (sometimes referred to as "workpiece processing sheet") that includes a substrate and an adhesive layer, and then undergo processes such as back grinding, dicing, cleaning, drying, wafer expansion, picking up, and assembly.

For example, a back-polished semiconductor wafer is attached to a sheet and then diced on the sheet. Dicing converts the semiconductor wafer into multiple semiconductor chips. The multiple semiconductor chips are then individually picked up from the sheet.

Furthermore, in other methods, after the above-mentioned cutting, the plurality of semiconductor wafers supported on the aforementioned sheet are transferred to another sheet, and the plurality of semiconductor wafers are individually picked up from the other sheet.

Devices such as die ejectors can be used to pick up semiconductor wafers from the wafer, as described above. This device pushes the semiconductor wafers upwards individually from the other wafers from a surface on the wafer opposite to the surface to which they are attached. Pushing a semiconductor wafer upwards in this way makes it easier to pick it up using a collet. Furthermore, expanding the wafer as needed to create gaps between the semiconductor wafers makes pushing upwards and picking them up even easier.

One method of pushing the semiconductor chip upwards is using one or more pins or needles. In this method, the tip of the pin or needle contacts the wafer at a point, pushing the semiconductor chip upwards. However, in recent years, with the thinning of semiconductor chips and the development of using harder and easier-to-cut materials as semiconductor materials, semiconductor chips have become more brittle. When handling such semiconductor chips, if the upward push of the pin or needle is too large, it may damage the semiconductor chip.

On the other hand, UV-curable adhesives are mostly used as the adhesive layer in the aforementioned workpiece processing wafers. With UV-curable adhesives, the adhesive layer can be irradiated with UV light before picking up the semiconductor wafer to harden the adhesive and reduce adhesive strength. Therefore, the semiconductor wafer can be easily picked up from the adhesive layer. However, from a process or semiconductor wafer type perspective, there are cases where non-UV-curable adhesives are required. In these cases, achieving good pick-up performance is more challenging than when using UV-curable adhesives.

Patent 1 discloses a cutting film in which, to obtain suitable sheet expansion and excellent pick-up properties, the substrate comprises a specific random polypropylene (A) and a specific olefin elastomer (B), and a 100% tensile stress is set on the specific olefin elastomer (B). [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent No. 5494132

[The problem the invention aims to solve]

Incidentally, when the predetermined processing steps are completed, the workpiece machining sheet is peeled off from the adhered material. At this time, static electricity, called stripping charge, is generated between the workpiece machining sheet and the adhered material. This static electricity causes dust and other substances to adhere to the workpiece and the device, and also leads to damage to the workpiece and the device. Therefore, the workpiece machining sheet also needs to be antistatic.

Furthermore, after the semiconductor wafer dicing process, the resulting wafers are typically cleaned. Specifically, a workpiece wafer carrying multiple wafers is adsorbed and fixed on a rotary table, and the wafers are cleaned using ultrapure water and subsequently dried (air-dried). After these processes are completed, the workpiece wafer carrying multiple wafers is separated from the rotary table, and the inventors have confirmed that stripping charges are also generated during this separation process.

However, as described in Patent Document 1, conventional workpiece processing sheets do not address antistatic properties and suffer from the aforementioned problem of deionization.

This invention was made in view of this situation, with the aim of providing a workpiece machining sheet that exhibits excellent pick-up and excellent antistatic properties even when using an active energy radiation non-curing adhesive layer. [Means for solving the problem]

To achieve the above objectives, firstly, the present invention provides a workpiece processing sheet, which comprises a substrate and an adhesive layer deposited on one surface of the substrate. The substrate comprises a surface layer located near the adhesive layer, a back layer located away from the adhesive layer, and an intermediate layer located between the surface layer and the back layer. The adhesive layer comprises an active energy radiation non-curing adhesive. The surface layer and the back layer contain an antistatic agent. The tensile stress at elongation of 20% and 50% when the substrate is subjected to a tensile test at a temperature of 23°C and a relative humidity of 50%RH is 8 MPa or more and 30 MPa or less (Invention 1).

In the above-described invention (Invention 1), since the surface layer and the back layer contain antistatic agents, they possess excellent antistatic properties. Furthermore, since the surface layer contains antistatic agents and the substrate has the aforementioned tensile properties, even when using an active energy radiation non-curing adhesive in the adhesive layer, excellent pick-up performance is achieved when picking up the wafer from the workpiece processing wafer.

In the above invention (Invention 1), the aforementioned non-hardening adhesive with active energy rays is preferably an acrylic adhesive (Invention 2).

In the above inventions (Inventions 1 and 2), it is preferable that the aforementioned surface layer, the aforementioned intermediate layer and the aforementioned back layer each contain at least one of polyolefin resin and olefin thermoplastic elastomer (Invention 3).

In the above inventions (Inventions 1 to 3), it is preferable that the intermediate layer does not contain an antistatic agent, or that the intermediate layer contains an antistatic agent in a smaller amount (unit: mass %) than the surface layer and the back layer (Invention 4).

In the above inventions (Inventions 1 to 4), it is preferable that the antistatic agent is a polymeric antistatic agent (Invention 5).

In the above inventions (Inventions 1 to 5), the surface resistivity of the surface of the adhesive layer opposite to the substrate is preferably 1.0 × ^10¹³ Ω/□ or less (Invention 6).

Of the above inventions (Inventions 1-6), it is preferred as a cutting disc (Invention 7). [Invention Benefits]

According to the present invention, the workpiece processing sheet can exhibit excellent pickup and excellent antistatic properties even when using an active energy ray non-curing adhesive in the adhesive layer.

[The form in which the invention is implemented]

The embodiments of the present invention will now be described. Figure 1 shows a cross-sectional view of a workpiece processing sheet according to one embodiment of the present invention. The workpiece processing sheet 1 shown in Figure 1 includes a substrate 11 and an adhesive layer 12 deposited on one surface of the substrate 11.

As shown in FIG1, the substrate 11 includes a surface layer 111 located near the adhesive layer 12, a back layer 113 located away from the adhesive layer 12, and an intermediate layer 112 located between the surface layer 111 and the back layer 113.

In the workpiece processing sheet 1 according to this embodiment, the adhesive layer 12 is composed of an active energy radiation non-curing adhesive, and the surface layer 111 and the back layer 113 contain an antistatic agent. Furthermore, when the substrate 11 is subjected to a tensile test at a temperature of 23°C and a relative humidity of 50%RH, the tensile stress at elongation of 20% and 50% is 8 MPa or more and 30 MPa or less; the physical property related to tensile stress is sometimes referred to as "tensile property". In addition, the specific measurement method for the tensile test in this specification is described in the test examples below.

The workpiece processing sheet 1 according to this embodiment has excellent antistatic properties because its surface layer 111 and back layer 113 contain antistatic agents. Therefore, it can effectively suppress the stripping charge when separating the stripping sheet or workpiece from the workpiece processing sheet 1. Furthermore, after cleaning and drying the workpiece on the workpiece processing sheet 1, it can also effectively prevent the stripping charge when separating the workpiece processing sheet 1 from the rotary table.

Furthermore, according to this embodiment, the workpiece processing sheet 1 has an antistatic agent in its surface layer 111 and the substrate 11 has the aforementioned tensile properties. Therefore, even when using an active energy radiation non-hardening adhesive in the adhesive layer 12, it exhibits excellent pick-up performance when picking up a wafer from the workpiece processing sheet 1. Specifically, the ejector pin or needle used to push the wafer upward during pickup can have a smaller upward pushing amount. As a result, damage to the wafer caused by the upward pushing step can be effectively suppressed. The reason why excellent pick-up performance can be obtained due to the aforementioned tensile properties of the substrate 11 is that the substrate 11 becomes relatively hard, making it difficult to conform to the wafer being picked up, thereby allowing the wafer to be peeled off from the adhesive layer. Furthermore, it is unclear why the surface layer 111 contains an antistatic agent, which enables excellent pick-up properties, but it can be assumed that the adhesive force of the adhesive layer 12 is reduced due to some effect.

From the viewpoint of obtaining excellent pick-up properties, the tensile stress of the substrate 11 in this embodiment at tensile elongation of 20% and 50% in the above tensile test is 8 MPa or more, and preferably 8.5 MPa or more. Furthermore, also from the viewpoint of obtaining excellent pick-up properties, the tensile stress is 30 MPa or less, preferably 20 MPa or less, and particularly preferably 15 MPa or less.

From the viewpoint of obtaining excellent pick-up properties, the tensile stress of the substrate 11 in this embodiment at a tensile elongation of 10% in the tensile test is preferably 7.5 MPa or more, and particularly preferably 8 MPa or more. Furthermore, also from the viewpoint of obtaining excellent pick-up properties, the tensile stress at a tensile elongation of 10% is preferably 20 MPa or less, and particularly preferably 15 MPa or less.

1. Structure of the workpiece processing sheet 1-1. Substrate As described above, the substrate 11 in this embodiment includes a surface layer 111, an intermediate layer 112, and a back layer 113.

(1) Surface Layer In the workpiece processing sheet 1 according to this embodiment, the surface layer 111 contains an antistatic agent. In this way, excellent antistatic properties are achieved, while also improving pick-up performance.

The antistatic agent used in this embodiment is not particularly limited, and known antistatic agents can be used. Examples of antistatic agents include low-molecular-weight antistatic agents and high-molecular-weight antistatic agents, but from the viewpoint of obtaining excellent pick-up properties and not easily bleeding out from the formed layer, high-molecular-weight antistatic agents are preferred.

Examples of polymeric antistatic agents include copolymers containing polyether units, such as polyether esteramides and polyether polyolefin block copolymers. These copolymers may also contain metal salts such as alkali metal salts and alkaline earth metal salts, as well as ionic liquids.

The content of the antistatic agent in the surface layer 111 is preferably 3% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. This results in superior antistatic properties and pick-up performance. Furthermore, this content is preferably 40% by mass or less, particularly preferably 35% by mass or less, and even more preferably 30% by mass or less. This makes it easier to meet the aforementioned tensile properties.

The materials other than the antistatic agent constituting the surface layer 111 are not particularly limited as long as they meet the aforementioned tensile properties. However, to meet these tensile properties, it is preferable to contain at least one of polyolefin resins and olefin thermoplastic elastomers (hereinafter sometimes referred to as "olefin elastomers"), and it is particularly preferable to contain at least polyolefin resins and, if necessary, further olefin elastomers or other thermoplastic elastomers. Based on these components, it becomes easier to meet the aforementioned tensile properties, and the pick-up properties become more excellent.

Furthermore, in this specification, the term "polyolefin resin" refers to a homopolymer or copolymer with olefins as monomers, or a copolymer with olefins and other molecules as monomers, wherein the mass percentage of the olefin-based portion in the polymerized resin is 1.0% by mass or more. Moreover, "olefin elastomer" is a copolymer containing structural units derived from olefins or their derivatives (olefin compounds), which is a material that exhibits rubber-like elasticity and thermoplasticity within a temperature range including room temperature.

Polyolefin resins are not particularly limited as long as they do not impede the aforementioned stretching properties and achieve the desired effect. The polymers constituting polyolefin resins can be linear or have side chains. Furthermore, they can contain aromatic rings or aliphatic rings.

Examples of olefin monomers constituting polyolefin resins include olefin monomers with 2 to 8 carbon atoms, α-olefin monomers with 3 to 18 carbon atoms, and olefin monomers with cyclic structures. Examples of olefin monomers with 2 to 8 carbon atoms include ethylene, propylene, 2-butene, and octene. Examples of α-olefin monomers with 3 to 18 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, and 1-octane. Examples of cyclic olefin monomers include norbornene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, tetracyclododecene, and their derivatives.

These polyolefin resins can be used alone or in combination of two or more.

Among the specific examples of the above-mentioned polyolefin resins, it is preferred to use at least one of polyethylene containing ethylene as the main polymer unit and polypropylene containing propylene as the main polymer unit.

The polypropylene mentioned above generally includes homopolymer polypropylene, random polypropylene, and block polypropylene. These can be used individually or in combination of two or more. In this embodiment, from the viewpoint of easily and effectively performing flake-forming, random polypropylene is preferred.

When polyolefin resins contain polyethylene, the polyethylene can be any of high-density polyethylene, medium-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, and linear low-density polyethylene, or a mixture of two or more of these.

The content of polyolefin resin in the surface layer 111 is preferably 20% by mass or more, particularly preferably 23% by mass or more, and even more preferably 25% by mass or more. Furthermore, this content is preferably 60% by mass or less, particularly preferably 58% by mass or less, and even more preferably 56% by mass or less. Since the content of polyolefin resin is within the above range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up properties become more superior.

Examples of olefinic elastomers include compounds comprising at least one resin selected from the group consisting of ethylene-propylene copolymers, ethylene-α-olefin copolymers, propylene-α-olefin copolymers, butene-α-olefin copolymers, ethylene-propylene-α-olefin copolymers, ethylene-butene-α-olefin copolymers, propylene-butene-α-olefin copolymers, and ethylene-propylene-butene-α-olefin copolymers. Among the above, ethylene-propylene copolymers are preferred.

When the surface layer 111 contains an olefinic elastomer, the content of the olefinic elastomer in the surface layer 111 is preferably 25% by mass or more, particularly preferably 30% by mass or more, and even more preferably 35% by mass or more. Furthermore, this content is preferably 75% by mass or less, particularly preferably 70% by mass or less, and even more preferably 65% by mass or less. Since the content of the olefinic elastomer in the surface layer 111 is within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up properties become more superior.

Surface layer 111 preferably contains a thermoplastic elastomer other than olefinic elastomers, particularly styrene-based thermoplastic elastomers (hereinafter sometimes referred to as "styrene-based elastomers"). Styrene-based elastomers are copolymers containing structural units derived from styrene or its derivatives (styrene compounds), and are materials that exhibit rubber-like elasticity and thermoplasticity over a temperature range including room temperature. Because surface layer 111 contains styrene-based elastomers, the generation of cutting discs during cutting can be reduced.

As styrene-based elastomers, examples include styrene-conjugated diene copolymers and styrene-olefin copolymers, with styrene-conjugated diene copolymers being preferred. Specific examples of styrene-conjugated diene copolymers include unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymers, styrene-butadiene-styrene copolymers (SBS), styrene-butadiene-butene-styrene copolymers, styrene-isoprene copolymers, styrene-isoprene-styrene copolymers (SIS), and styrene-ethylene-isoprene-styrene copolymers; hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene/propylene-styrene copolymers (SEPS: hydrogenated styrene-isoprene-styrene copolymers), styrene-ethylene-butene-styrene copolymers (SEBS: hydrogenated styrene-butadiene copolymers), and styrene-ethylene/ethylene-propylene-styrene copolymers (SEEPS). Styrene-based thermoplastic elastomers can be either hydrogenated (hydrogenation products) or unhydrogenated, with hydrogenated products being preferred. Among the above, from the viewpoint of easily achieving the aforementioned tensile properties, hydrogenated styrene-conjugated diene copolymers are preferred, and styrene-ethylene/ethylene-propylene-styrene copolymers (SEEPS) are particularly preferred.

In styrene-based elastomers, the content of structural units derived from styrene or styrene-based compounds is preferably 5% by mass or more, particularly preferably 7% by mass or more, and even more preferably 10% by mass or more. Furthermore, the content of the aforementioned structural units is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less. Because the content of the aforementioned structural units falls within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties.

When the surface layer 111 contains a styrene-based elastomer, the content of the styrene-based elastomer in the surface layer 111 is preferably 5% by mass or more, and particularly preferably 10% by mass or more. Furthermore, this content is preferably 40% by mass or less, particularly preferably 30% by mass or less, and even more preferably 20% by mass or less. Since the content of the styrene-based elastomer in the surface layer 111 is within the above-mentioned range, it becomes easier to meet the aforementioned tensile properties, and the generation of cutting discs during cutting can be reduced.

Surface layer 111 may also contain other components besides those mentioned above, such as the components of a substrate used in general workpiece processing sheets. Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. The content of these additives is not particularly limited, but it is preferable to keep it within a range that allows surface layer 111 to perform the desired function.

(2) Intermediate Layer In this embodiment, the material constituting the intermediate layer 112 is not particularly limited as long as it satisfies the aforementioned tensile properties. However, to satisfy these tensile properties, it is preferable to contain at least one of a polyolefin resin and an olefin elastomer, and particularly preferably, it contains at least a polyolefin resin and, if necessary, further contains an olefin elastomer or other thermoplastic elastomer. Based on these components, it becomes easier to satisfy the aforementioned tensile properties, and the pick-up properties become more superior.

Preferred examples of polyolefin resins, olefin elastomers and styrene elastomers are each the same as those listed in surface layer 111.

The content of polyolefin resin in the intermediate layer 112 is preferably 5% by mass or more, and particularly preferably 7% by mass or more. Furthermore, this content is preferably 95% by mass or less, and particularly preferably 90% by mass or less. Since the content of polyolefin resin in the intermediate layer 112 is within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up properties become more superior.

When the intermediate layer 112 contains an olefinic elastomer, the content of the olefinic elastomer in the intermediate layer 112 is preferably 10% by mass or more, particularly preferably 30% by mass or more, and even more preferably 50% by mass or more. Furthermore, this content is preferably 90% by mass or less, particularly preferably 80% by mass or less, and even more preferably 70% by mass or less. Since the content of the olefinic elastomer in the intermediate layer 112 is within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up properties become more superior.

When the intermediate layer 112 contains a styrene-based elastomer, the content of the styrene-based elastomer in the intermediate layer 112 is preferably 5% by mass or more, and particularly preferably 10% by mass or more. Furthermore, this content is preferably 30% by mass or less, and particularly preferably 20% by mass or less. Since the content of the styrene-based elastomer in the intermediate layer 112 is within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up properties become more superior.

Here, the intermediate layer 112 may also contain an antistatic agent, but the antistatic agent may soften the formed layer. Therefore, from a pick-up point of view, it is preferable that the intermediate layer 112 does not contain an antistatic agent. If the intermediate layer 112 contains an antistatic agent, it is preferable that the intermediate layer 112 contains a smaller amount (unit: mass%) of antistatic agent than the surface layer 111 and the back layer 113. Specifically, in the intermediate layer 112, the content is preferably less than 5% by mass, more preferably less than 3% by mass, particularly preferably less than 1% by mass, and best of all is 0% by mass. If the intermediate layer 112 contains an antistatic agent, the lower limit of its content is, for example, 0.01% by mass or more.

Similar to the surface layer 111, the intermediate layer 112 may also contain other components besides those described above, such as the components of a substrate used for general workpiece processing sheets.

(3) Back Layer In this embodiment, the back layer 113 contains an antistatic agent. This provides excellent antistatic properties.

As an antistatic agent in the back layer 113, the same antistatic agent as described in the description of the surface layer 111 can be used.

The content of the antistatic agent in the back layer 113 is preferably 3% by mass or more, particularly preferably 20% by mass or more, and even more preferably 30% by mass or more. This makes it easier to exhibit good antistatic properties. Furthermore, this content is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less. This makes it easier to achieve the aforementioned tensile properties.

The material other than the antistatic agent constituting the back layer 113 is not particularly limited as long as it meets the aforementioned tensile properties. However, to meet these tensile properties, it is preferable to contain at least one of polyolefin resins and olefin elastomers, and it is especially preferable to contain olefin elastomers, or polyolefin resins and olefin elastomers or other thermoplastic elastomers, particularly styrene elastomers. Based on these components, it becomes easier to meet the aforementioned tensile properties, and the pick-up properties become more excellent.

Preferred examples of polyolefin resins, olefin elastomers and styrene elastomers are each the same as those listed in surface layer 111.

When the back layer 113 contains polyolefin resin, the content of polyolefin resin in the back layer 113 is preferably 20% by mass or more, particularly preferably 25% by mass or more, and even more preferably 30% by mass or more. Furthermore, this content is preferably 85% by mass or less, particularly preferably 80% by mass or less, and even more preferably 75% by mass or less. Since the content of polyolefin resin in the back layer 113 is within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up properties become more superior.

When the back layer 113 contains an olefinic elastomer, the content of the olefinic elastomer in the back layer 113 is preferably 30% by mass or more, particularly preferably 40% by mass or more, and even more preferably 50% by mass or more. Furthermore, this content is preferably 85% by mass or less, particularly preferably 80% by mass or less, and even more preferably 75% by mass or less. Since the content of the olefinic elastomer in the back layer 113 is within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up performance becomes superior.

When the back layer 113 contains a styrene-based elastomer, the content of the styrene-based elastomer in the back layer 113 is preferably 5% by mass or more, and particularly preferably 10% by mass or more. Furthermore, this content is preferably 40% by mass or less, particularly preferably 30% by mass or less, and even more preferably 20% by mass or less. Since the content of the styrene-based elastomer in the back layer 113 is within the above-mentioned range, it becomes easier to achieve the aforementioned tensile properties, and the pick-up performance becomes superior.

Similar to the surface layer 111 and the intermediate layer 112, the back layer 113 may also contain other components besides those described above, such as the components of a substrate used for general workpiece processing sheets.

(4) Surface Treatment of the Substrate To improve adhesion to the adhesive layer 12, the surface of the substrate 11 to which the adhesive layer 12 will be deposited may be treated with a primer, corona treatment, plasma treatment, or roughening treatment (matte finish). For example, roughening treatments include embossing and sandblasting. Of these, corona treatment is preferred.

(5) Method for Manufacturing the Substrate The method for manufacturing the substrate 11 in this embodiment is not particularly limited. For example, melt extrusion molding methods such as the T-die method and the circular die method can be used; calendering molding methods; solution methods such as dry methods and wet methods can be used. Of the above, from the viewpoint of efficiently manufacturing the substrate, melt extrusion is preferred, and the T-die method is particularly preferred.

Furthermore, when the substrate 11 is manufactured using melt extrusion molding, the components constituting each layer can be mixed separately, and the resulting mixture can be directly or after being made into granules, and then a known extrusion molding machine can be used to simultaneously extrude (co-extrude) multiple layers to form a film.

(6) Substrate Properties, etc. (6-1) Thickness In this embodiment, the thickness of the surface layer 111 is preferably 10 μm or less, particularly 8 μm or less, and even more preferably 4 μm or less. As described above, because the surface layer 111 near the adhesive layer 12 is thin, it is easier to satisfy the aforementioned tensile properties while achieving the desired antistatic properties.

Furthermore, the thickness of the surface layer 111 is preferably 1 μm or more, especially 2 μm or more, and even better if it is 3 μm or more. This makes it easier to achieve good antistatic properties and improves pickup performance.

In this embodiment, the thickness of the intermediate layer 112 is preferably 40 μm or more, particularly preferably 50 μm or more, and even more preferably 60 μm or more. This makes it easier to meet the aforementioned tensile properties and improves pick-up performance. Furthermore, the workpiece processing sheet 1 easily possesses appropriate strength and effectively supports the workpiece fixed to it. The thickness of the intermediate layer 112 is preferably 100 μm or less, particularly preferably 90 μm or less, and even more preferably 80 μm or less. This makes it easier to meet the aforementioned tensile properties.

In this embodiment, the thickness of the back layer 113 is preferably 2 μm or more, particularly preferably 4 μm or more, and even more preferably 8 μm or more. This improves the antistatic properties of the workpiece processing sheet 1. Furthermore, the thickness of the back layer 113 is preferably 40 μm or less, particularly preferably 30 μm or less, and even more preferably 25 μm or less. This makes it easier to meet the aforementioned tensile properties.

In this embodiment, the overall thickness of the substrate 11 is preferably 50 μm or more, particularly preferably 60 μm or more, and even more preferably 70 μm or more. Furthermore, the thickness is preferably 140 μm or less, particularly preferably 120 μm or less, and even more preferably 100 μm or less. Since the overall thickness of the substrate 11 is within the above-mentioned range, it becomes easier to meet the aforementioned tensile properties, and it becomes easier to effectively support the workpiece fixed on the workpiece processing sheet 1.

(6-2) Surface Resistivity: The surface resistivity of the surface of the surface layer 111 in the substrate 11 is preferably 1.0 × ^10¹³ Ω/□ or less, particularly preferably 1.0 × ^10¹² Ω/□ or less, and even more preferably 1.0 × ^10¹¹ Ω/□ or less. In this way, the workpiece processing sheet 1 according to this embodiment can exhibit excellent antistatic properties. Furthermore, there is no particular limitation on the lower limit of the above-mentioned surface resistivity; for example, it can be 1.0 × ^10⁸ Ω/□ or more, and particularly preferably 1.0 × ^10⁹ Ω/□ or more. Details of the surface resistivity measurement method in this specification are described in the experimental examples described later.

1-2. Adhesive Layer The adhesive used in the adhesive layer 12 of this embodiment is a non-curing adhesive with active energy radiation. There are no particular limitations on the type of non-curing adhesive, as long as it exhibits sufficient adhesive force to the adherend (especially sufficient adhesive force to the workpiece for machining). Examples of non-curing adhesives with active energy radiation include acrylic adhesives, rubber adhesives, polysiloxane adhesives, polyurethane adhesives, polyester adhesives, and polyvinyl ether adhesives. Among these, acrylic adhesives are preferred from the viewpoint of easily achieving the desired adhesive force.

Acrylic adhesives used as active energy radiation non-curing adhesives are preferably composed of an acrylic copolymer (A) and a crosslinking agent (B). The acrylic copolymer (A) preferably comprises structural units derived from functionalized monomers and structural units derived from (meth)acrylate monomers or their derivatives. Furthermore, in this specification, the term (meth)acrylate means both acrylic acid and methacrylic acid. Other similar terms are also used in this manner.

As a structural unit of the acrylic copolymer (A), a monomer containing a functional group is preferred, preferably a monomer with a polymerizable double bond, hydroxyl group, carboxyl group, amino group, substituted amino group, epoxy group, or other functional group within the molecule. Among the above, a monomer containing a hydroxyl group within the molecule that uses a crosslinking agent (B), particularly a monomer with excellent reactivity with isocyanate crosslinking agents as described later, is preferred.

Examples of monomers containing hydroxyl groups include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate. These materials can be used alone or in combination of two or more.

In the acrylic copolymer (A), the content of the structural units derived from the functionalized monomers is preferably 3% by mass or more, and particularly preferably 7% by mass or more. Furthermore, in the acrylic copolymer (A), the content of the structural units derived from the functionalized monomers is preferably 20% by mass or less, and particularly preferably 15% by mass or less. Since the content of the structural units derived from the functionalized monomers is within the above-mentioned range, an adhesive having a predetermined adhesive strength and a suitable crosslinking density can be obtained.

From the viewpoint of adhesion, it is preferable to use alkyl methacrylates with 1 to 20 carbon atoms as the methacrylate monomers constituting the acrylic copolymer (A). Examples of alkyl methacrylates with 1 to 20 carbon atoms include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, n-decyl methacrylate, n-dodecyl methacrylate, myristyl methacrylate, palmitate methacrylate, stearyl methacrylate, etc.

Of the above, from the viewpoint of effectively imparting adhesive force, alkyl methacrylates with 1 to 12 carbon atoms in the alkyl group are preferred, and alkyl acrylates with 1 to 10 carbon atoms in the alkyl group are particularly preferred. Specifically, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, and 2-ethylhexyl methacrylate are preferred examples. The above materials can be used alone or in combination of two or more.

Of the above, the combination of methyl methacrylate and 2-ethylhexyl methacrylate, particularly methyl methacrylate and 2-ethylhexyl acrylate, is preferred. This readily yields an adhesive with an excellent balance between adhesive strength and pick-up properties. A mass ratio of 5:95 to 25:75 is preferred.

In the acrylic copolymer (A), the content of the structural unit derived from the (meth)acrylate monomer is preferably 70% by mass or more, and particularly preferably 75% by mass or more. Furthermore, in the acrylic copolymer (A), the content of the structural unit derived from the (meth)acrylate monomer is preferably 97% by mass or less, and particularly preferably 90% by mass or less.

The functionalized monomers described above can be copolymerized with (meth)acrylate monomers or their derivatives using conventional methods to obtain acrylic copolymers (A). In addition to these monomers, dimethacrylamide, vinyl acetate, styrene, etc. can also be copolymerized.

The weight-average molecular weight (Mw) of the acrylic copolymer (A) is preferably 300,000 or higher, particularly 400,000 or higher, and even more preferably 500,000 or higher. Furthermore, the weight-average molecular weight (Mw) is preferably 1.5 million or lower, particularly 1.2 million or lower, and even more preferably 1 million or lower. This makes it easier to obtain an adhesive with an excellent balance between adhesive strength and pick-up properties. Additionally, the weight-average molecular weight (Mw) in this specification is a value converted from standard polystyrene measured by gel permeation chromatography (GPC).

As a crosslinking agent (B), any crosslinking agent that can react with the functional groups of the acrylic copolymer (A) is acceptable. Examples include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, and ammonium salt crosslinking agents. Furthermore, crosslinking agent (B) can be used alone or in combination with two or more other crosslinking agents.

In this case, where the acrylic copolymer (A) includes monomers containing hydroxyl groups as structural monomer units, it is preferable to use an isocyanate crosslinker (B) that has excellent reactivity with hydroxyl groups.

Isocyanate crosslinkers contain at least polyisocyanate compounds. Examples of polyisocyanate compounds include, for instance, aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; biuret bodies and isocyanurate bodies; and adducts of the above-mentioned reaction products with low molecular weight, active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. From the perspective of reactivity with hydroxyl groups, it is preferable to use trihydroxymethylpropane-modified aromatic polyisocyanates, and trihydroxymethylpropane-modified toluene diisocyanate and trihydroxymethylpropane-modified xylene diisocyanate are particularly preferred.

The amount of crosslinker (B) is preferably 0.1 parts by weight or more, particularly preferably 1 part by weight or more, and even more preferably 3 parts by weight or more, relative to 100 parts by weight of the acrylic copolymer (A). Furthermore, the amount of crosslinker (B) is preferably 20 parts by weight or less, particularly preferably 15 parts by weight or less, and even more preferably 10 parts by weight or less, relative to 100 parts by weight. Since the amount of crosslinker (B) is within the above-mentioned range, an adhesive with a predetermined adhesive strength and a suitable crosslinking density can be obtained.

In this embodiment, the thickness of the adhesive layer 12 is preferably 1 μm or more, particularly preferably 3 μm or more, and even more preferably 5 μm or more. Furthermore, the thickness of the adhesive layer 12 is preferably 50 μm or less, particularly preferably 30 μm or less, and even more preferably 15 μm or less. Since the thickness of the adhesive layer 12 is within the above-mentioned range, a good balance between adhesive strength and pick-up performance can be achieved.

1-3. Peel-off sheet In the workpiece processing sheet 1 according to this embodiment, before attaching the surface of the adhesive layer 12 opposite to the substrate 11 (hereinafter sometimes referred to as the "adhesive surface") to the workpiece, a peel-off sheet may be deposited on that surface to protect it.

The aforementioned peeling sheet can have any structure, such as a structure in which a plastic film is peeled using a peeling agent. Specific examples of such plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and polyolefin films such as polypropylene and polyethylene. As the aforementioned peeling agent, polysiloxanes, fluorinated compounds, long-chain alkyl compounds, etc., can be used; among these, polysiloxanes, which are inexpensive and provide stable performance, are preferred.

There are no particular restrictions on the thickness of the above-mentioned peeling sheets; for example, it can be above 16μm or below 250μm.

1-4. Other In the workpiece processing sheet 1 according to this embodiment, an adhesive layer may also be deposited on the surface of the adhesive layer 12 opposite to the substrate 11. In this case, the workpiece processing sheet 1 according to this embodiment can be used as a cutting and wafer bonding sheet. In this sheet, a workpiece can be attached to the surface of the adhesive layer opposite to the adhesive layer 12, and the adhesive layer and the workpiece can be cut together to obtain a wafer with a monomerized adhesive layer deposited on it. The wafer can then be easily fixed to the object on which the wafer will be mounted by means of this monomerized adhesive layer. The materials used to constitute the adhesive layer are preferably those containing thermoplastic resins and low-molecular-weight thermosetting adhesive components, or those containing B-stage (semi-cured) thermosetting adhesive components.

Furthermore, in the workpiece processing sheet 1 according to this embodiment, a protective film forming layer may also be deposited on the adhesive surface of the adhesive layer 12. In this case, the workpiece processing sheet 1 according to this embodiment can be used as a protective film forming and cutting sheet. In this sheet, a workpiece can be attached to the surface of the protective film forming layer opposite to the adhesive layer 12, and the protective film forming layer and the workpiece can be cut together to obtain a wafer with a monomerized protective film forming layer deposited. As the workpiece, it is preferable to use a workpiece with a circuit formed on one surface. In this case, the protective film forming layer is usually deposited on the surface opposite to the surface where the circuit is formed. This allows the monomeric protective film layer to harden over a predetermined time, thereby forming a sufficiently durable protective film on the wafer. The protective film layer is preferably composed of an uncured curable adhesive.

2. Manufacturing Method of the Workpiece Machining Sheet The manufacturing method of the workpiece machining sheet 1 according to this embodiment is not particularly limited. For example, it is preferable to obtain the workpiece machining sheet 1 by forming an adhesive layer 12 on a surface of the adhesive layer 12 opposite to the surface of the peeling sheet after forming an adhesive layer 12 on the surface of the substrate 11.

The adhesive layer 12 can be formed using known methods. For example, a coating solution containing an adhesive composition for forming the adhesive layer 12 and, as needed, a solvent or dispersion medium can be added. The coating solution is then applied to a peelable surface (hereinafter sometimes referred to as a "peelable surface") of the peeling sheet. The adhesive layer 12 can then be formed by drying the resulting coating.

The coating liquid described above can be applied using known methods, such as bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating. Furthermore, the properties of the coating liquid are not particularly limited as long as it can be applied; it may contain components used to form the adhesive layer 12 as a solute, or components used as a dispersion medium. Moreover, a release liner can be used as a process material for peeling, or it can be used to protect the adhesive layer 12 until it adheres to the substrate.

When the adhesive composition used to form the adhesive layer 12 includes the aforementioned crosslinking agent, it is preferable to change the aforementioned drying conditions (temperature, time, etc.) or to perform additional heat treatment, so that the polymer component in the coating film undergoes a crosslinking reaction with the crosslinking agent, thereby forming a crosslinked structure with the desired density within the adhesive layer 12. Furthermore, in order to ensure that the aforementioned crosslinking reaction proceeds sufficiently, the adhesive layer 12 may be left to stand for several days, for example, at an environment of 23°C and a relative humidity of 50%, after being bonded to the substrate 11, to allow it to mature.

3. Method of Using the Workpiece Machining Sheet The workpiece machining sheet 1 according to this embodiment can be used for machining workpieces such as semiconductor wafers. That is, after attaching the adhesive surface of the workpiece machining sheet 1 according to this embodiment to the workpiece, machining can be performed on the workpiece machining sheet 1. The workpiece machining sheet 1 according to this embodiment can be used as a back-grinding sheet, a dicing sheet, an expansion sheet, a pick-up sheet, etc., depending on the machining process. Examples of workpieces include semiconductor components such as semiconductor wafers and semiconductor packages, and glass components such as glass plates.

As mentioned above, the workpiece processing sheet 1 according to this embodiment is preferably used as a sheet material in a process that includes at least a picking process because of its excellent pick-up performance. For example, it can be a cutting sheet used from the cutting process to the picking process, or a transfer sheet for transferring the wafer obtained after cutting and using it in the picking process.

Furthermore, the workpiece processing sheet 1 according to this embodiment, as described above, possesses excellent antistatic properties. The workpiece processing sheet 1 according to this embodiment can suppress stripping charges during the separation of the stripping sheet or the separation of the workpiece. Moreover, the workpiece processing sheet 1 according to this embodiment can also effectively suppress stripping charges when the workpiece processing sheet is separated from the rotary table after cleaning and drying of the wafer while the workpiece processing sheet is fixed on the rotary table. Therefore, the workpiece processing sheet 1 according to this embodiment is also suitable for such cleaning and drying processes.

Furthermore, when the workpiece processing sheet 1 according to this embodiment includes the aforementioned adhesive layer, the workpiece processing sheet 1 can be used as a cutting and wafer bonding sheet. Additionally, when the workpiece processing sheet 1 according to this embodiment includes the aforementioned protective film forming layer, the workpiece processing sheet 1 can be used as a protective film forming and cutting sheet.

The embodiments described above are for the purpose of facilitating understanding of the present invention and are not intended to limit the present invention. Therefore, it means that the elements disclosed in the above embodiments also include all design variations and equivalents that fall within the technical scope of the present invention.

For example, other layers may be deposited between the substrate 11 and the adhesive layer 12, or on the surface of the substrate 11 opposite to the adhesive layer 12, according to the workpiece processing sheet 1 of this embodiment. Furthermore, other layers may be deposited on the surface of the surface layer 111 opposite to the intermediate layer 112, between the surface layer 111 and the intermediate layer 112, between the intermediate layer 112 and the back layer 113, and on the surface of the back layer 113 opposite to the intermediate layer 112. [Embodiment]

The invention will now be explained in more detail through examples, etc., but the scope of the invention is not limited to these examples, etc.

[Example 1] (1) Preparation of the Substrate 28 parts by weight of random polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., product name "Novatec FX3B"), 42 parts by weight of olefinic elastomer (manufactured by Nippon Polypropylene Co., Ltd., product name "Welnex RFX4V"), and 30 parts by weight of polymeric antistatic agent (manufactured by Sanyo Chemical Co., Ltd., product name "Pelectron PVH") were dried separately and then mixed using a twin-screw mixer to obtain granules for the surface layer.

Furthermore, 38 parts by weight of random polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., product name "Novatec FX3B") and 62 parts by weight of olefin elastomer (manufactured by Nippon Polypropylene Co., Ltd., product name "Welnex RFX4V") are dried separately and then mixed using a twin-screw mixer to obtain granules for the intermediate layer.

65 parts by weight of an olefinic elastomer (manufactured by Japan Polypropylene Co., Ltd., product name "Welnex RFX4V") and 35 parts by weight of a polymeric antistatic agent (manufactured by Sanyo Chemical Co., Ltd., product name "Pelectron PVH") were dried separately and then mixed using a twin-screw mixer to obtain granules for the back layer.

Using the three granules obtained above, co-extrusion molding was performed using a small T-die extruder (manufactured by Toyo Precision Machinery Manufacturing Co., Ltd., product name "Laboplast Mill") to obtain a three-layer substrate structure formed by sequentially stacking a surface layer with a thickness of 4μm, an intermediate layer with a thickness of 68μm, and a back layer with a thickness of 4μm.

(2) Formulation of the Adhesive Composite A (meth)acrylate polymer (A) was prepared by solution polymerization of 78 parts by weight of 2-ethylhexyl acrylate, 12 parts by weight of methyl methacrylate, and 10 parts by weight of 2-hydroxyethyl acrylate. The weight-average molecular weight (Mw) of this (meth)acrylate polymer was determined to be 800,000 by methods described later.

100 parts by weight of the (meth)acrylate polymer obtained above (converted to solid content, the same below) and 4.7 parts by weight of trihydroxymethylpropane-modified toluene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate L") as a crosslinking agent were mixed in a solvent to obtain an adhesive coating solution.

(3) Formation of the Adhesive Layer The adhesive composition obtained in step (2) above was applied to a release sheet (manufactured by Lintec, product name "SP-PET381031"), wherein the release sheet was obtained by forming a polysiloxane-based release agent layer on one surface of a 38 μm thick polyethylene terephthalate film, and dried at 90°C for 1 minute to obtain a laminate with an adhesive layer (a) of 5 μm thickness formed on the release sheet.

(4) Fabrication of the Adhesive Sheet A corona treatment is applied to the surface of the substrate obtained in step (1) above, on the side of the surface layer, and then bonded to the surface of the adhesive layer in the laminate obtained in step (3) above to obtain a sheet for workpiece processing.

Here, the aforementioned weight-average molecular weight (Mw) is the weight-average molecular weight converted from standard polystyrene, measured using gel permeation chromatography (GPC) under the following conditions: <Measurement Conditions> • Measuring apparatus: HLC-8320 manufactured by Tosoh Corporation • GPC column (passing in the following order): Manufactured by Tosoh Corporation TSK gel super H-H TSK gel super HM-H TSK gel super H2000 • Measuring solvent: tetrahydrofuran • Measuring temperature: 40℃

[Examples 2-4, Comparative Example 1] Except for changing the composition of the granules used to form the substrate and the thickness of each layer as shown in Table 1, the workpiece processing sheet is manufactured in the same manner as in Example 1.

In addition, in Example 2, 15 parts by weight of styrene-ethylene/ethylene-propylene-styrene block copolymer (SEEPS) (manufactured by Kuraray, "HYBRAR-7311F", styrene ratio: 12% by weight) were formulated as styrene-based elastomers in the surface layer, intermediate layer and back layer, respectively.

Furthermore, in Comparative Example 1, 15 parts by weight of maleic anhydride adduct of ethylene-ethyl acrylate copolymer as an acid-modified resin (manufactured by SK Functional Polymer, product name "BONDINE LX4110", ethyl acrylate content: 5% by weight, acid content: 3% by weight) were further incorporated into the surface layer.

[Example 5] Except for changing the composition of the granules used to form the substrate and the thickness of each layer as shown in Table 1, the substrate (same as the substrate in Example 4) is manufactured in the same manner as in Example 1. On the other hand, except for changing the amount of crosslinking agent to 4.2 parts by weight, the adhesive layer is formed in the same manner as in Example 1 to obtain a laminate with an adhesive layer (b) of 5 μm thickness formed on the peel sheet. Using the above substrate and the laminate, a workpiece processing sheet is manufactured in the same manner as in Example 1.

[Example 6] Except for changing the composition of the granules used to form each layer of the substrate and the thickness of each layer as shown in Table 1, the substrate is manufactured in the same manner as in Example 1 (same as the substrate in Example 4). On the other hand, except for changing the amount of crosslinking agent to 3.8 parts by weight, the adhesive layer is formed in the same manner as in Example 1 to obtain a laminate with an adhesive layer (c) of 5 μm thickness formed on the peel sheet. Using the above substrate and the laminate, a workpiece processing sheet is manufactured in the same manner as in Example 1.

[Comparative Example 2] Using the same apparatus as in Example 1, a film composed of a single layer of ethylene-methacrylic acid copolymer (manufactured by Mitsui-Dow Polychemicals, product name "Nucrel N0903HC") was produced. The surface of the resulting film on the side where the adhesive layer is deposited was irradiated with an electron beam of 10 kGy for 2.2 seconds once, and this was used as a substrate. Using this substrate, a workpiece processing sheet was manufactured in the same manner as in Example 1.

[Comparative Example 3] Using the same apparatus as in Example 1, a film composed of a single layer of ethylene-methacrylic acid copolymer (manufactured by Mitsui-Dow Polychemicals, product name "Nucrel N0903HC") was produced. The surface of the resulting film on the side where the adhesive layer was deposited was irradiated twice with an electron beam of 10 kGy for 2.2 seconds each time, and this was used as a substrate. Using this substrate, a workpiece processing sheet was manufactured in the same manner as in Example 1.

[Experimental Example 1] (Tensive Test) The substrates manufactured in the Examples and Comparative Examples were cut into 10mm × 120mm test pieces, and the tensile stress was measured according to JIS K7161:2014 at a temperature of 23°C and a relative humidity of 50%RH. Specifically, the test pieces were subjected to a tensile testing machine (manufactured by Shimadzu Corporation, product name "Autograph") with the chuck distance set to 100mm and a speed of 200mm/min. The tensile stress (MPa) at elongation of 10%, 20%, and 50% was measured. Measurements were also taken in the extrusion direction (MD direction) during substrate molding. The results are shown in Table 2.

[Experimental Example 2] (Evaluation of Pickup Capabilities) Silicon wafers were prepared to be ground to 150μm using a grinder (manufactured by Disco, product name "DFG8540") at #2000.

After the peeling sheet is peeled off from the workpiece processing sheet manufactured in the embodiments and comparative examples, the exposed surface of the adhesive layer is attached to the polished surface of the silicon wafer using a tape applicator (manufactured by Lintec Corporation, product name "Adwill RAD2500m/12"). Next, a cutting ring frame is attached to the edge portion of the exposed surface of the workpiece processing sheet (the portion that does not overlap with the silicon wafer). Furthermore, the workpiece processing sheet is cut along the outer diameter of the ring frame.

Next, using a dicing apparatus (manufactured by Disco, product name "DFD6362"), the silicon wafer was diced under the following conditions to monomerize it into wafers with dimensions of 10mm × 10mm. <Diceing Conditions> Wafer thickness: 150μm Instrument blade: Manufactured by Disco, product name "ZH05-SD2000-N1-50 CC" Instrument blade speed: 30000rpm Diceing speed: 60mm/sec Instrument blade height: 0.060mm Cooling water flow rate: 1.0L/min Cooling water temperature: 20℃

Four hours and 24 hours after the workpiece was attached to the silicon wafer, a pick-up device (manufactured by Canon Machinery, product name "BESTEM D02") was used to pick up the wafer from the workpiece under the following pick-up conditions. The required upward push of the ejector pins during wafer pick-up was then measured. The results are shown in Table 2. <Pick-up Conditions> • Pick-up method: 4 ejector pins • Pick-up speed: 5 mm/s • Ejector pin upward push: 550–800 μm

Based on the measured ejector pin push-up amount, the pickup capability was evaluated according to the following criteria. The evaluation results are shown in Table 2. ○: Ejector pin push-up amount is less than 600mm ╳: Ejector pin push-up amount exceeds 600mm

[Experimental Example 3] (Measurement of Surface Resistivity) The workpiece processing sheets manufactured in the Embodiments and Comparative Examples were cut into 100mm × 100mm pieces to serve as samples for surface resistivity measurement. After adjusting the humidity of these samples for 24 hours at 23°C and 50% RH, the surface resistivity (Ω/□) of the surface layer side was measured using a digital electroderter (manufactured by Advantest) at an applied voltage of 100V. The results are shown in Table 2.

[Experimental Example 4] (Evaluation of Antistatic Properties) The workpiece processing sheet manufactured in the Examples and Comparative Examples was cut into B4 size pieces and used as samples. The peeling sheet was peeled off the sample at a speed of 10 cm/s. Using a voltmeter (manufactured by Prostat, product name "fold meter PFM-711A"), the voltage (V) of the sample immediately after peeling was measured from the substrate side. Then, the antistatic properties were evaluated based on the following criteria. The antistatic properties and evaluation results are shown in Table 2. ○: Voltage below 1V. ╳: Voltage exceeding 1V.

[Table 1] Implementation Example 1 Implementation Example 2 Implementation Example 3 Implementation Example 4 Implementation Example 5 Implementation Example 6 Comparative example 1 Comparative example 2 Comparative example 3 substrate Thickness of each layer (surface layer/intermediate layer/back layer) (μm) 4/68/4 4/72/4 4/72/4 4/72/4 4/56/20 4/56/20 4/72/4 Single layer 80μm Single layer 80μm Composition (parts by weight) Surface layer polypropylene Novatec FX3B (manufactured by Nippon Polypropylene Co., Ltd.) 28 55 36 28 28 28 45 Nucrel N0903HC (manufactured by Mitsui & Dow Polymer Chemicals) irradiated once with an electron beam Nucrel N0903HC (manufactured by Mitsui & Dow Polymer Chemicals) irradiated twice with an electron beam Alkene elastomers Welnex RFX4V (manufactured by Japan Polypropylene Corporation) 42 - 59 37 37 37 15 Styrene-based elastomers HYBRAR-7311F (manufactured by Kuraray Corporation) - 15 - - - - - Acid-modified resins BONDINE LX4110 (manufactured by SK Functional Polymer) - - - - - - 15 Antistatic agent Pelectron PVL (manufactured by Sanyo Chemical Co., Ltd.) - 30 5 - - - - Pelectron PVH (manufactured by Sanyo Chemical Co., Ltd.) 30 - - 35 35 35 25 middle layer polypropylene Novatec FX3B (manufactured by Nippon Polypropylene Co., Ltd.) 38 85 38 10 10 10 28 Alkene elastomers Welnex RFX4V (manufactured by Japan Polypropylene Co., Ltd.) 62 - 62 90 90 90 39 Styrene-based elastomers HYBRAR-7311F (manufactured by Kuraray Corporation) - 15 - - - - 33 Back layer polypropylene Novatec FX3B (manufactured by Nippon Polypropylene Co., Ltd.) - 55 36 - - - - Alkene elastomers Welnex RFX4V (manufactured by Japan Polypropylene Co., Ltd.) 65 - 59 65 65 65 70 Styrene-based elastomers HYBRAR-7311F (manufactured by Kuraray Corporation) - 15 - - - - - Antistatic agent Pelectron PVL (manufactured by Sanyo Chemical Co., Ltd.) - 30 5 - - - - Pelectron PVH (manufactured by Sanyo Chemical Co., Ltd.) 35 - - 35 35 35 30 Types of adhesive layers a a a a b c a a a

[Table 2] Tensile stress (MPa) Picking Surface resistivity (Ω/□) Antistatic properties Elongation at break 10% Elongation at break 20% Elongation at break (TEP) 50% After 4 hours Apply 24 hours later evaluate The surface of the substrate layer Voltage (V) evaluate Upward thrust (μm) Upward thrust (μm) Implementation Example 1 10.4 11.1 9.0 600 600 ○ 4.7 x ^10⁹ 0.23 ○ Implementation Example 2 9.5 10.7 9.6 600 600 ○ 1.5 x 10 ¹⁰ 0.25 ○ Implementation Example 3 11.4 11.9 9.2 550 550 ○ 5.4x 10 ¹¹ 0.33 ○ Implementation Example 4 10.6 11.2 8.8 550 550 ○ 3.9 x ^10⁹ 0.23 ○ Implementation Example 5 10.6 11.2 8.8 550 550 ○ 3.9 x ^10⁹ 0.22 ○ Implementation Example 6 10.6 11.2 8.8 600 600 ○ 3.8 x ^10⁹ 0.23 ○ Comparative example 1 7.3 7.9 6.9 650 650 ╳ 7.6 x ^10⁹ 0.16 ○ Comparative example 2 7.8 10.0 14.1 600 600 ○ 9.6 x 10 ^{^14} 16.0 ╳ Comparative example 3 8.6 11.7 17.3 600 600 ○ 4.9x 10 ¹⁴ 17.0 ╳

Table 2 clearly shows that the workpiece machining sheet manufactured in the embodiment exhibits excellent pick-up performance and antistatic properties. [Industrial Applicability]

The workpiece processing wafer of this invention can be used for processing workpieces such as semiconductor wafers.

1: Workpiece processing sheet 11: Substrate 12: Adhesive layer 111: Surface layer 112: Intermediate layer 113: Backing layer

Figure 1 is a cross-sectional view of a workpiece processing sheet according to one embodiment of the present invention.

1: Workpiece machining sheet

11: Substrate

12: Adhesive layer

111: Surface layer

112:Middle layer

113: Back layer

Claims (7)

A workpiece processing sheet comprising a substrate and an adhesive layer deposited on one surface of the substrate, wherein the substrate comprises a surface layer near the adhesive layer, a back layer away from the adhesive layer, and an intermediate layer between the surface layer and the back layer, and the adhesive layer comprises an active energy radiation non-curing adhesive, the surface layer and the back layer contain an antistatic agent, and wherein the tensile stress at elongation of 20% and 50% when the substrate is subjected to a tensile test at a temperature of 23°C and a relative humidity of 50%RH is 8 MPa or more and 30 MPa or less. The workpiece processing sheet as described in claim 1, wherein the aforementioned active energy radiation non-hardening adhesive is an acrylic adhesive. The workpiece processing sheet as described in claim 1, wherein the aforementioned surface layer, the aforementioned intermediate layer and the aforementioned back layer each contain at least one of polyolefin resin and olefin thermoplastic elastomer. The workpiece processing sheet as described in claim 1, wherein the aforementioned intermediate layer does not contain an antistatic agent, or the aforementioned intermediate layer contains an antistatic agent in a smaller amount (unit: mass %) than the aforementioned surface layer and the aforementioned back layer. The workpiece processing sheet as described in claim 1, wherein the aforementioned antistatic agent is a polymeric antistatic agent. The workpiece processing sheet as described in claim 1, wherein the surface resistivity of the surface of the aforementioned adhesive layer opposite to the substrate is 1.0 × ^10¹³ Ω/□ or less. The workpiece processing disc described in any of claims 1 to 6 is a cutting disc.